>Draconian error-handling is appropriate in such scenarios. However, way too many people are hand-writing HTML - and it's way too hard to generate sensible HTML - to be able to make that plausible.
I find it fascinating that people are willing to accept string syntax checking hand-written for JavaScript but not for HTML.
You can bounce radio signals off the ionosphere with fairly simple equipment, if you have a ham radio license you can do it too. The interesting thing is that not everything is known about the ionosphere. For example, an open question is whether Long-Delayed Echoes exist or not, or whether they are just Backscatter, or if they are real.
This TAG finding is all the more reason for the W3C to support declarative approaches to markup, which allow you to express intent in markup, and leave another level to convert that intent to presentation. This approach starts at the top with technologies such as CSS, but the need for dynamic pages is better addressed by recent additions such as XBL (here's an example in mozilla -- think of it as like CSS but binding to script instead of to a fixed set of attributes) and XForms (think of it as a 3-layer model for the web page -- data, logic, and presentation).
SLAC is kind enough to allow the Foothiils Amateur Radio Society to hold a monthly outdoor/indoor amateur radio symposium and operating event there, called AmTech Day. Now that no morse code test is required for any level of amateur license in the US, it's a great time to get into amateur radio and experiment with digital communications, microwave technology, satellites, or even Maker style operations such as bouncing radio waves off the ionosphere with equipment you can build yourself.
Here are some other resources to check out. Any of these would be better than a 500-in-1 kit, and all are cheaper.
Elmer101
a tutorial on radio theory with practical experiments. Think of it as a grown-up's version (you are a grown-up, right?) of the 500-in-1 manual. It's based on an existing design, a transceiver kit from Small Wonder Labs, and so you can read it and do experiements with with your own parts or with the kit. [A ham license to use these kits no longer requires a morse code test, just a 35-question written Technician exam.]
QRPKits.com. This site runs the gamut for easy radio kits from simple transmitters to software-defined radio.
Nuts and Volts magazine, a great resource, with a good coverage of general electronics, radio, robotics, microprocessors.
Circuit Cellar magazine, descended from Steve's Circuit Cellar column in the old Byte magazine. Slightly more in depth articles, but fewer areas of coverage.
>As long as people hold back on the upgrade to IE7 (or Firefox / Opera), the Internet at large will remain stunted. You should write W3C and ask for them to proceed with plans for moving the web forward. Currently, they've bowed to pressure from WHATWG (a group formed by incumbent minor browser vendors) to require future upgrades to all be backwards compatible, including specifying rules for parsing broken web pages and requiring all future standards to support them.
Curiously, there's never a call from these same quarters for laxity in JavaScript syntax, nor any complaints there.
> I distinctly remember George Bush promising broadband for all by 2007. Yes, because the energy companies told the republican party to put "Broadband over Power Lines" into their platform. you can explore the various versions of the platform at archive.org and see that it was specifically called out, I believe even with particular technology providers mentioned. Then I guess somebody realized that picking technology winners was anti-republican-sounding so they took it out and replaced it with the more mealy-mouthed "broadband for all." Then Michael Powell as FCC Chair blasted the energy companies' proposals to use the power lines as giant radio antennas through, over the written-but-quietly-retracted objections of the NTIA (the part of the executive branch that allocates radio to non-military government users), agreed to notch out the military frequencies (they have guns) and rode rough-shod over everyone else. And the new FCC chair repeats the promise that BPL will provide internet access to rural customers, when in fact, it won't and it isn't economically feasible to do it that way.
I am completely confused by your reply. You seem to think I'm both a neo-conservative and a communist. Either that's because I suggested that you can legally use SSH over the Internet (didn't know what was a neocon view), or it was my suggestion that your incitement to civil disobedience (by using encryption over radio spectrum where federal law disallows it) was tilting at windmills and not likely to change anything other than getting you in trouble.
>WhatWGs stuff...is XForms on steroids I don't think WHATWG's work is XForms on steroids, and I don't think WHATWG thinks it either. WHATWG explicitly rejects XML and explicitly rejects the separation of data from presentation (if I understand what I read correctly). Their emphasis is on incremental addition of attributes to HTML4 to add new behaviors that add incremental value but aren't required.
XForms starts with the premise that XML is the data format, and that you want to keep your data in one place (XForms calls them "instances"; you might think of them as loadable XML data islands if you're doing XMLHTTPRequest stuff).
In the HTML head, you declare the instances, give each an id attribute, and populate them either inline or by a src attribute with a URL. Then you write the UI in the body, using input elements for input, output elements for outputting values inline in text, and a few other controls for menus and sliders. For each of these form controls, you specify which part of which instance you want it bound to with a "ref" attribute using a pathname-like notation (/a/b/c would give you the nested element "c", for example).
When the user interacts with the form controls, it changes the values in the XML data. If you have two controls bound to the same place in data, they'll both change at once.
Eventually, you'll want to submit your data; you do this by writing a "submission" element in the head with many of the same attributes that are on the HTML "form" element (action, method, etc.). When you press a submit button tied to one of these submissions, it POST the data (usually as XML though you have control) back to the server. You have the option to take back the response to this POST as another XML document, and leave your who web page alone...just the data changes. (You can think of this as postback-free posting.) The UI automagically adjusts to the changes in the data, and if the data changes its whole shape, for example, you have have different divs of your UI appear automatically based on what XML appears.
Want to know more? Take a look at the http://en.wikibooks.org/wiki/XForms site or read one of the online books on XForms from O'Reilly or Addison-Wesley.
I don't think the calculator is a particularly good example; the person who wrote it encoded the state machine of the keys by switching entire bindings in and out.
Recently I wrote an entire webmail application with a small PHP back end that outputs the mailbox list, the message list, and individual messages as XML (each addressed by a URL using the REST methodology -- XForms works very well with REST). The UI, written entirely in XHTML+XForms, is 300 lines.
There's a little bit of JavaScript used to supplement the basic markup, using Mozilla's XBL to make it output dates in a human-readable format. (Mozilla XForms ought to do this anyway, and when it does, it will likely ship as XBL with JavaScript and CSS to bind it).
Try XForms. It's vendor independent, standard, and aims to obviate 80% of scripting. In the Mozilla implementation, it uses XBL to allow you to write behind-the-scenes JavaScript (a la XUL) to implement presentation stuff that keys off the appearance and data type declarations to enhance the presentation.
You jumped from my example (the small chance of uninformed people accidentally interfering with critical or life-saving radio communications multiplied by the large number of such people if there were no technical tests and licensing) to your example (that terrorism exists), and then claimed that because terrorism exists, we shouldn't have any laws that might be circumvented. Given this viewpoint, it's not hard for me to see that you believe that all you have to do is add encryption, and you've got total security. But the physical world isn't an SSH tunnel, and shared resources (air, radio spectrum, the 25 MPH zone in front of the elementary school) are all protected by government because they need to be.
Go ahead and use SSH over the Internet; there's plenty of bandwidth there, and you aren't going to be causing anybody problems. I'm old enough to remember when we didn't have the privilege of using crypto across borders, and I'm glad we do now.
But please, for your own safety, don't act on your naive belief that "the right to hide what you're doing [is] more important than the FCC's right to control."
> Why do we need a license for that? > As long as you don't interfere with someone else's communications, there's no need for a license. > Big Brother is bad enough with not allowing encryption, but requiring a license, well that itself was the foot in the door.
Good point! Why do we even need a license for driving?
As long as you don't run into someone else's car, there's no need for a license.
Of course, with radio, your signal can propagate around the world in 50 milliseconds, so you do have a few billion more potential someone elses to worry about...
But really, what are the chances that an unlicensed person would accidentally transmit on a frequency in use by an aircraft instrument landing system anyway?
Who needs government protection for airplanes anyway? Can't they defend themselves? Give 'em all rockets. An armed society is a polite society. Now, if you knew your jamming transmission of a pizza order to your brother-in-law's delivery service might result in an RPG aimed at your antenna, you'd be sure not to interfere. Very satisfying and much better than a piddly test that requires demonstrating understanding the technology involved and the regulations.
The Wall Street Journal's Walter S. Mossberg's latest column apparently missed a writeup on a existing software system called Emacs. Emacs is software written by Humans. The software allows Windows, Linux, Mac, BSD, Amiga, ITS, TOPS-20, Solaris, HP-UX, Multics, DOS, and Apple ][ users to do common tasks, like launching programs, spellchecking (M-$), or Googling (W3M) for search terms, but what's interesting is that it allows you to do these tasks by use of the keyboard. From the article: 'There are many implementations of Emacs products, which can be downloaded anywhere. One, called Emacs, allows you edit text, Java, C++, C#, Lisp, Perl, XML, HTML, Relax NG, ADA, and other obscure languages, to launch programs and switch among windows via typed commands, do spell-checking, and to look up the meaning of words. Most versuins of Emacs also include a simple calculator and the ability to launch Google searches.' Humans are already able to write their own commands for Emacs using the ELisp extension language, not only in current versions, but in all versions all the way back to the pre-GNU ITS version (which itself then used TECO as the extension language.
Don't forget RF as an introduction to electronics. If you want to know about series and parallel circuits and light bulbs, stick with DC and batteries. You mentioned capacitors and other components...understanding the behavior of RF circuits is part and parcel of understanding what a capacitor is for. Even digital designers need to know about RF circuits, so starting there can complement the understanding you probably already have of digital logic from programming.
Of course, I think the best way to learn about RF is through ham radio. Many hams are currently active in QRP (low-power or simple radio) operation, including design and construction. The circuits are small enough that you can breadboard them, and the people who design them often take great care to describe how things work, and how to hack them.
In fact, a formal course with a book written by Prof. David Rutledge of Cal Tech ("The Electronics of Radio") uses a simple ham radio transceiver as the basis for its introduction. The book at the kit are both still available.
Getting a ham radio license can be an entre to a group of people who do this kind of thing and are used to helping each other. Now that the morse code requirement is lifted, you may find it easier to get a license. If you've gone through Forrest M Mimms III's books, you probably know about half of what you need already. See here for some roadmap info, or here for practice versions of the real tests, or here for a tutorial approach to the tests.
I can type 30 WPM on my hiptop, and could do the same on the Motorola T900. I suspect Blackberry users feel the same. Does anybody remember the Chiclet Keyboard controversy of the late 1970'sand 1980's (Commodore PET, TI Home Computer?) Jobs ought to -- he was there, and the Apple ][ had a real keyboard. (Well, it couldn't display lower case, but at least the keyboard worked.)
90%+ is possible for waveguides, and for open-wire feedline, but is usually lower for coaxial feedline. VF is 1/sqrt(dielectric constant). Interestingly, the velocity itself is VF*c=1/sqrt(L*C) where c=speed of light in a vacuum, and L and C are the series inductance and shunt capacitance of the feedline, so those values are directly related to the velocity factor. Finally, given L and C we can calculate the characteristic impedance Z=sqrt(L/C).
The characteristic impedance of the coax is important to achieve maximum power transfer.
Another interesting thing nobody mentioned from the paper is that they say you can create an antenna by extending the center line out of the coax; presumably this is done with a 1/4 wavelength, though they specifically refer to this as matching to the impedance of free space, which we all know is 120*pi = ~377 Ohms. This number again is calculated by the sqrt(L/C) formula, but using L/m (magnetic permeability) and C/m (permittivity) which are both constants, so it's a little unfair.
You can do other fascinating calculations using transmission line equations. In fact, the paper says that the experimenters verified some of their findings by using larger scale components and microwave experiments.
So, if you're interested in the math behind, you can do it at home using standard coax and RF yourself, and get a flavor. Now that there's no more morse code test involved for getting a ham radio, it would be a good time to check out getting your ham license with just written tests of knowledge, and start doing experiments with practical results.
I've been using RedHat since 5.0, and remember the great service they did with the 1.0 disk drives pre-loaded you could order. But lately it seems like RPM has stagnated, and Fedora appears to be confused as to its direction, and finally, the upgrades have been getting harder lately. Ubuntu is one of the first Debian derivatives that seems to work as well as RedHat has done, with well-done installers, etc. I suspect that with the handwriting on the wall about upgrade support from the Legacy project, my next upgrade will be to Ubuntu.
>I'll just add to my previous comment that it was once widely believed that long wave radio signals propagate the longest distance, then for a while that idea was less well believed....
Terms such as "short wave" and "long wave" have largely passed into disuse, replaced by High Frequency (roughly short wave) and Medium Frequency (roughly long wave), and then for mostly point-point communications, VHF, UHF, and above.
Except for the exotic moonbounce and tropospheric ducting mentioned, all long distance radio communications on this planet uses various layers of the ionosphere, and depends on ionosphereic reflection and refraction, and is thus dependent on the state of the Sun, which has an 11-year up-down cycle. We're going to reach rock bottom in 2007, and then things will start looking up again.
If you want to see what frequency is best for reliable communications around the globe, check out this site and look at the map closest to you. These maps are compiled using ionosondes, and represent hourly experiments. They will tell you what frequency in the HF has the best chance of bouncing off the ionosphere and reach the destination. The NVIS map at the top is for transmitting straight up and having your signal come down in a ~250 mile radius. The maps below that, centered on cities around the world (San Francisco, Sydney, etc.) will show you what you need to do to get a signal to or from those cities. There's no quality info, but if you want current solar conditions, see the Propfire plugin, which will tell you.
The Cuban station mentioned in the article sounds like the cut-numbers station, which sends 5-letter groups that are morse code numbers, but shortened. So instead of 1 (*----) they send A (*-), and instead of 2 (**---) they send U (**-), and 3 (***--) becomes V (***-), etc.
Lest you think all these secret stations are foreign, here's the story of Yosemite Sam, a station that transmitted "I'm a gonna get you, you varmint!" followed by a quick digital BRAP sound, and how it was traced by enterprising hams to a US military-industrial facility.
Slashdot Mirror
>Draconian error-handling is appropriate in such scenarios. However, way too many people are hand-writing HTML - and it's way too hard to generate sensible HTML - to be able to make that plausible.
I find it fascinating that people are willing to accept string syntax checking hand-written for JavaScript but not for HTML.
You can bounce radio signals off the ionosphere with fairly simple equipment, if you have a ham radio license you can do it too. The interesting thing is that not everything is known about the ionosphere. For example, an open question is whether Long-Delayed Echoes exist or not, or whether they are just Backscatter, or if they are real.
This TAG finding is all the more reason for the W3C to support declarative approaches to markup, which allow you to express intent in markup, and leave another level to convert that intent to presentation. This approach starts at the top with technologies such as CSS, but the need for dynamic pages is better addressed by recent additions such as XBL (here's an example in mozilla -- think of it as like CSS but binding to script instead of to a fixed set of attributes) and XForms (think of it as a 3-layer model for the web page -- data, logic, and presentation).
Take a look at the Web Accessibility roadmap from the W3C, and in particular the section on intent-based markup.
SLAC is kind enough to allow the Foothiils Amateur Radio Society to hold a monthly outdoor/indoor amateur radio symposium and operating event there, called AmTech Day. Now that no morse code test is required for any level of amateur license in the US, it's a great time to get into amateur radio and experiment with digital communications, microwave technology, satellites, or even Maker style operations such as bouncing radio waves off the ionosphere with equipment you can build yourself.
>"Heathkit". Damn, I miss that company.
Try Elecraft.
a tutorial on radio theory with practical experiments. Think of it as a grown-up's version (you are a grown-up, right?) of the 500-in-1 manual. It's based on an existing design, a transceiver kit from Small Wonder Labs, and so you can read it and do experiements with with your own parts or with the kit. [A ham license to use these kits no longer requires a morse code test, just a 35-question written Technician exam.]
WA5ZNU
>As long as people hold back on the upgrade to IE7 (or Firefox / Opera), the Internet at large will remain stunted.
You should write W3C and ask for them to proceed with plans for moving the web forward.
Currently, they've bowed to pressure from WHATWG (a group formed by incumbent minor browser vendors) to require future upgrades to all be backwards compatible, including specifying rules for parsing broken web pages and requiring all future standards to support them.
Curiously, there's never a call from these same quarters for laxity in JavaScript syntax, nor any complaints there.
Interested in doing your own experimentation at 10GHz and up but don't own a TV station yourself?
Try reading about it here or here.
> I distinctly remember George Bush promising broadband for all by 2007.
Yes, because the energy companies told the republican party to put "Broadband over Power Lines" into their platform.
you can explore the various versions of the platform at archive.org and see that it was specifically called out, I believe even with particular technology providers mentioned. Then I guess somebody realized that picking technology winners was anti-republican-sounding so they took it out and replaced it with the more mealy-mouthed "broadband for all." Then Michael Powell as FCC Chair blasted the energy companies' proposals to use the power lines as giant radio antennas through, over the written-but-quietly-retracted objections of the NTIA (the part of the executive branch that allocates radio to non-military government users), agreed to notch out the military frequencies (they have guns) and rode rough-shod over everyone else. And the new FCC chair repeats the promise that BPL will provide internet access to rural customers, when in fact, it won't and it isn't economically feasible to do it that way.
I am completely confused by your reply. You seem to think I'm both a neo-conservative and a communist. Either that's because I suggested that you can legally use SSH over the Internet (didn't know what was a neocon view), or it was my suggestion that your incitement to civil disobedience (by using encryption over radio spectrum where federal law disallows it) was tilting at windmills and not likely to change anything other than getting you in trouble.
>WhatWGs stuff...is XForms on steroids
I don't think WHATWG's work is XForms on steroids, and I don't think WHATWG thinks it either. WHATWG explicitly rejects XML and explicitly rejects the separation of data from presentation (if I understand what I read correctly). Their emphasis is on incremental addition of attributes to HTML4 to add new behaviors that add incremental value but aren't required.
XForms starts with the premise that XML is the data format, and that you want to keep your data in one place (XForms calls them "instances"; you might think of them as loadable XML data islands if you're doing XMLHTTPRequest stuff).
In the HTML head, you declare the instances, give each an id attribute, and populate them either inline or by a src attribute with a URL. Then you write the UI in the body, using input elements for input, output elements for outputting values inline in text, and a few other controls for menus and sliders. For each of these form controls, you specify which part of which instance you want it bound to with a "ref" attribute using a pathname-like notation (/a/b/c would give you the nested element "c", for example).
When the user interacts with the form controls, it changes the values in the XML data. If you have two controls bound to the same place in data, they'll both change at once.
Eventually, you'll want to submit your data; you do this by writing a "submission" element in the head with many of the same attributes that are on the HTML "form" element (action, method, etc.). When you press a submit button tied to one of these submissions, it POST the data (usually as XML though you have control) back to the server. You have the option to take back the response to this POST as another XML document, and leave your who web page alone...just the data changes. (You can think of this as postback-free posting.) The UI automagically adjusts to the changes in the data, and if the data changes its whole shape, for example, you have have different divs of your UI appear automatically based on what XML appears.
Want to know more? Take a look at the http://en.wikibooks.org/wiki/XForms site or read one of the online books on XForms from O'Reilly or Addison-Wesley.
I don't think the calculator is a particularly good example; the person who wrote it encoded the state machine of the keys by switching entire bindings in and out.
Recently I wrote an entire webmail application with a small PHP back end that outputs the mailbox list, the message list, and individual messages as XML (each addressed by a URL using the REST methodology -- XForms works very well with REST). The UI, written entirely in XHTML+XForms, is 300 lines.
There's a little bit of JavaScript used to supplement the basic markup, using Mozilla's XBL to make it output dates in a human-readable format.
(Mozilla XForms ought to do this anyway, and when it does, it will likely ship as XBL with JavaScript and CSS to bind it).
See http://graflex.org/klotz/2006/11
Try XForms. It's vendor independent, standard, and aims to obviate 80% of scripting.
In the Mozilla implementation, it uses XBL to allow you to write behind-the-scenes JavaScript (a la XUL) to implement presentation stuff that keys off the appearance and data type declarations to enhance the presentation.
See http://en.wikibooks.org/wiki/XForms
You jumped from my example (the small chance of uninformed people accidentally interfering with critical or life-saving radio communications multiplied by the large number of such people if there were no technical tests and licensing) to your example (that terrorism exists), and then claimed that because terrorism exists, we shouldn't have any laws that might be circumvented. Given this viewpoint, it's not hard for me to see that you believe that all you have to do is add encryption, and you've got total security. But the physical world isn't an SSH tunnel, and shared resources (air, radio spectrum, the 25 MPH zone in front of the elementary school) are all protected by government because they need to be.
Go ahead and use SSH over the Internet; there's plenty of bandwidth there, and you aren't going to be causing anybody problems. I'm old enough to remember when we didn't have the privilege of using crypto across borders, and I'm glad we do now.
But please, for your own safety, don't act on your naive belief that "the right to hide what you're doing [is] more important than the FCC's right to control."
> Why do we need a license for that?
> As long as you don't interfere with someone else's communications, there's no need for a license.
> Big Brother is bad enough with not allowing encryption, but requiring a license, well that itself was the foot in the door.
Good point! Why do we even need a license for driving?
As long as you don't run into someone else's car, there's no need for a license.
Of course, with radio, your signal can propagate around the world in 50 milliseconds, so you do have a few billion more potential someone elses to worry about...
But really, what are the chances that an unlicensed person would accidentally transmit on a frequency in use by an aircraft instrument landing system anyway?
Who needs government protection for airplanes anyway? Can't they defend themselves? Give 'em all rockets. An armed society is a polite society. Now, if you knew your jamming transmission of a pizza order to your brother-in-law's delivery service might result in an RPG aimed at your antenna, you'd be sure not to interfere. Very satisfying and much better than a piddly test that requires demonstrating understanding the technology involved and the regulations.
I saw take your idea and run with it!
The Wall Street Journal's Walter S. Mossberg's latest column apparently missed a writeup on a existing software system called Emacs. Emacs is software written by Humans. The software allows Windows, Linux, Mac, BSD, Amiga, ITS, TOPS-20, Solaris, HP-UX, Multics, DOS, and Apple ][ users to do common tasks, like launching programs, spellchecking (M-$), or Googling (W3M) for search terms, but what's interesting is that it allows you to do these tasks by use of the keyboard. From the article: 'There are many implementations of Emacs products, which can be downloaded anywhere. One, called Emacs, allows you edit text, Java, C++, C#, Lisp, Perl, XML, HTML, Relax NG, ADA, and other obscure languages, to launch programs and switch among windows via typed commands, do spell-checking, and to look up the meaning of words. Most versuins of Emacs also include a simple calculator and the ability to launch Google searches.' Humans are already able to write their own commands for Emacs using the ELisp extension language, not only in current versions, but in all versions all the way back to the pre-GNU ITS version (which itself then used TECO as the extension language.
Don't forget RF as an introduction to electronics. If you want to know about series and parallel circuits and light bulbs, stick with DC and batteries. You mentioned capacitors and other components...understanding the behavior of RF circuits is part and parcel of understanding what a capacitor is for. Even digital designers need to know about RF circuits, so starting there can complement the understanding you probably already have of digital logic from programming.
Of course, I think the best way to learn about RF is through ham radio. Many hams are currently active in QRP (low-power or simple radio) operation, including design and construction. The circuits are small enough that you can breadboard them, and the people who design them often take great care to describe how things work, and how to hack them.
In fact, a formal course with a book written by Prof. David Rutledge of Cal Tech ("The Electronics of Radio") uses a simple ham radio transceiver as the basis for its introduction. The book at the kit are both still available.
Other simpler Kits and projects are available at
http://qrpkits.com/
http://www.njqrp.org/ (try their CD ROM of back issues of HomeBrewer magazine)
http://www.norcalqrp.org/ (which is having an informal meeting this Saturday in Sunnyvale, CA if you're in Silicon Valley)
http://4sqrp.com/
For online peer groups, you might try reading the archives of some of th Yahoo groups; there are about 4500 on amateur radio. Or try these:
http://mailman.qth.net/mailman/listinfo/qrp-l
http://qrp-l.org/
Getting a ham radio license can be an entre to a group of people who do this kind of thing and are used to helping each other. Now that the morse code requirement is lifted, you may find it easier to get a license. If you've gone through Forrest M Mimms III's books, you probably know about half of what you need already. See here for some roadmap info, or here for practice versions of the real tests, or here for a tutorial approach to the tests.
I can type 30 WPM on my hiptop, and could do the same on the Motorola T900. I suspect Blackberry users feel the same.
Does anybody remember the Chiclet Keyboard controversy of the late 1970'sand 1980's (Commodore PET, TI Home Computer?) Jobs ought to -- he was there, and the Apple ][ had a real keyboard. (Well, it couldn't display lower case, but at least the keyboard worked.)
90%+ is possible for waveguides, and for open-wire feedline, but is usually lower for coaxial feedline.
VF is 1/sqrt(dielectric constant). Interestingly, the velocity itself is VF*c=1/sqrt(L*C) where c=speed of light in a vacuum, and L and C are the series inductance and shunt capacitance of the feedline, so those values are directly related to the velocity factor. Finally, given L and C we can calculate the characteristic impedance Z=sqrt(L/C).
The characteristic impedance of the coax is important to achieve maximum power transfer.
Another interesting thing nobody mentioned from the paper is that they say you can create an antenna by extending the center line out of the coax; presumably this is done with a 1/4 wavelength, though they specifically refer to this as matching to the impedance of free space, which we all know is 120*pi = ~377 Ohms. This number again is calculated by the sqrt(L/C) formula, but using L/m (magnetic permeability) and C/m (permittivity) which are both constants, so it's a little unfair.
You can do other fascinating calculations using transmission line equations. In fact, the paper says that the experimenters verified some of their findings by using larger scale components and microwave experiments.
So, if you're interested in the math behind, you can do it at home using standard coax and RF yourself, and get a flavor. Now that there's no more morse code test involved for getting a ham radio, it would be a good time to check out getting your ham license with just written tests of knowledge, and start doing experiments with practical results.
I've been using RedHat since 5.0, and remember the great service they did with the 1.0 disk drives pre-loaded you could order.
But lately it seems like RPM has stagnated, and Fedora appears to be confused as to its direction, and finally, the upgrades have been getting harder lately. Ubuntu is one of the first Debian derivatives that seems to work as well as RedHat has done, with well-done installers, etc. I suspect that with the handwriting on the wall about upgrade support from the Legacy project, my next upgrade will be to Ubuntu.
On September 2, 2006 I heard my own signal, a good fraction of a second later, twice in the span of a few seconds.
>I'll just add to my previous comment that it was once widely believed that long wave radio signals propagate the longest distance, then for a while that idea was less well believed....
Terms such as "short wave" and "long wave" have largely passed into disuse, replaced by High Frequency (roughly short wave) and Medium Frequency (roughly long wave), and then for mostly point-point communications, VHF, UHF, and above.
Except for the exotic moonbounce and tropospheric ducting mentioned, all long distance radio communications on this planet uses various layers of the ionosphere, and depends on ionosphereic reflection and refraction, and is thus dependent on the state of the Sun, which has an 11-year up-down cycle. We're going to reach rock bottom in 2007, and then things will start looking up again.
If you want to see what frequency is best for reliable communications around the globe, check out this site and look at the map closest to you. These maps are compiled using ionosondes, and represent hourly experiments. They will tell you what frequency in the HF has the best chance of bouncing off the ionosphere and reach the destination. The NVIS map at the top is for transmitting straight up and having your signal come down in a ~250 mile radius. The maps below that, centered on cities around the world (San Francisco, Sydney, etc.) will show you what you need to do to get a signal to or from those cities. There's no quality info, but if you want current solar conditions, see the Propfire plugin, which will tell you.
The Cuban station mentioned in the article sounds like the cut-numbers station, which sends 5-letter groups that are morse code numbers, but shortened.
So instead of 1 (*----) they send A (*-), and instead of 2 (**---) they send U (**-), and 3 (***--) becomes V (***-), etc.
Lest you think all these secret stations are foreign, here's the story of Yosemite Sam, a station that transmitted "I'm a gonna get you, you varmint!" followed by a quick digital BRAP sound, and how it was traced by enterprising hams to a US military-industrial facility.